Process for determining the lubricant power of lubricant oils

ABSTRACT

A process for determining the lubricant power of lubricant oils for slip-controlled clutches. In a test container (14) consisting of a double-walled, temperable vessel and filled with test lubricant oil, two friction partners (6, 8) are rotated against each other under a test load with practical conditions. A coefficient of friction characteristic curve (27, 28) is determined depending on the sliding speed. If in a working range (26) a progressive characteristic curve is obtained, the lubricant oil is suitable for use in slip-controlled clutches. Since the device required to carry out the process has a relatively simple structure and requires only a small amount of test lubricant oil, the process and device can be used to test production charges in lubricant oil development, during test bench or field tests and to test aging processes in a laboratory.

BACKGROUND OF THE INVENTION

The invention concerns a process for determining the lubricant power oflubricant oils.

The use of lubricant oils, especially lubricant oils called "automatictransmission fluids" (ATF), in a slip-controlled clutch presupposesaccurate knowledge of the friction value curve as a function of thesliding speed. If, in the operating range the curve of the frictionvalue, dependent on the sliding speed, does not correspond to aprogressive curve, it is thus expected that self-exciting frictionoscillations will occur in the vehicle. Thus, there is no longer anorderly working of slip-controlled clutches, for example, in regulatedconverter lock-up clutches.

As a rule, lubricant oils are evaluated, with regard to their fitnessfor use in slip-controlled clutches, by costly test benchsuperstructures with original installation parts. The values obtained,of course, should not be assigned at once to the lubricant power,rather, but not until after a certain service life of the lubricantoils. Further tests at regular intervals are needed, but not reasonablypossible in cost and time spent. For the same reasons, a widespreadanalysis in vehicle and/or components tests is mostly eliminated. Butthe knowledge of these values is indispensable when a long-term fitnessfor lubricant oils must be guaranteed.

The invention is based on the problem of providing a process and adevice with which the lubricant power of lubricant oils forslip-controlled clutches can be determined at a low cost so thatdecisive statements about a long-term fitness are possible.

SUMMARY OF THE INVENTION

No original installation parts are needed for the process and deviceaccording to the invention. Besides, only small quantities of oil, about100 ml, are required. Thereby, resulting in savings of cost and time inrelation to both the test bench structure and the performance of thetest. Thus, the lubricant power can now be detected together withvehicle or test bench tests, since only a small fragment of thelubricant oil is removed from the lubricant oil circuit for testingpurposes and the residual lubricant oil remains in the long-term test.

The amount of test oil is conveniently limited to less than 200 ml. Inaddition, the test container and the parts contained therein, such asthe specimen holder, etc., can be dimensioned accordingly so that evenwith small amounts of test oil the contact surfaces are alwayssufficiently supplied with test oil during the test. It is also possibleto situate additional displacement bodies in the test container in orderto obtain the desired amount of test oil. For the development ofadequate lubricant oils, it is of decisive importance to know the changeof the friction value characteristic as a function of the service life.With the process and corresponding device, according to the invention,it is possible to describe friction systems, such as existing inslip-controlled clutches, in relation to their coefficient of frictioncharacteristic curve in different states of processing and utilization.The process and device thus can be used in lubricants for control ofproduction charges in lubricant oil development during test bench orfield tests, to test aging processes in a laboratory and for evaluatingnew friction surfaces.

In the specification and in the claims, numerous features are shown anddescribed in combination. The expert will conveniently consider thecombined features also individually, depending on the problems to besolved, and form convenient added combinations.

BRIEF DESCRIPTION OF THE DRAWING(S)

An embodiment of the invention is shown in the drawing in which:

FIG. 1 diagrammatically shows a structure of a device according to theinvention;

FIG. 2 shows in enlarged view a range II in FIG. 1; and

FIG. 3 shows the coefficient of friction characteristic curves.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

A motor 1 drives, via a torque indicator 2, an input shaft 4, anequalizer connection 3, and a thrust washer 5 on which a ring disc 6 isfastened with a bolt 22. The ring disc 6 forms a friction partner andhas a ring surface 7 with which it abuts on another friction part. Thelatter is formed by a friction lining 8 which is superimposed on a mainbody 9. The main body 9 is screwed by means of a bolt 21 with a specimenholder 10 which is non-rotatably retained in a test container 14 by atorque support 16 and is supported tiltably towards all sides by a peakbearing 11. Instead of the peak bearing 11, which is formed by a doubletaper body, there can also be used a ball which meshes in correspondingcalottes of the adjacent parts.

The test container 14 is double walled and can be tempered so thatlubricant oils and friction pairs can be tested at different workingtemperatures. It is filled with test oil up to an oil level designatedwith 13.

The test container 14 rests on a test board 15. A load delivery system20 presses the test board 15 with the test container 10, the main body 9and the friction lining 8 against the ring surface 7 of the ring disc 6,via a lever mechanism 18, which flexibly supports itself on a foundation19.

The process, according to the invention, is carried out as follows:

The two friction partners formed by the ring disc 6 on one side and themain body 9 with the friction lining 8 on the other are clamped and thenthe test container 14 is filled with the test oil that is to be tested.Both friction parts essentially correspond to the friction pairs used inpractice. To test the friction pairs for the long-term fitness thereof,a reliable test oil of known properties is used as the test oil.

The alignment of the measured value sensors thus follows. To measure thenormal force, a dynamometer device 17 is integrated in the force flow,for example, as shown in FIG. 1, between the lever mechanism 18 and thetest board 15. The friction force is determined by means of a straingauge on the torque support 16. The input torque of the motor 1, whichis regulated by an external theoretical value transmitter on a presettheoretical speed, can be detected by means of the torque indicator 2and alternatively used to determine, even though with less accuracy, thefriction force. Thereafter the test load is applied, which by virtue ofthe peak bearing 11 and the connection 3, is distributed evenly over thering surface 7.

With a double-walled, temperature controllable vessel as the testcontainer 14, for which serves a temperature sensor, not shown, the testtemperature can be adjusted in the test container 14. When the testtemperature is reached, the introductory operation to form the frictionsurfaces on the ring surface 7 and on the friction lining 8 can bestarted. This is followed by the actual test cycle, wherein carried outis a series of measurements with several sliding speeds which have beenreset by the theoretical speed of the motor 1. The friction value ismathematically determined from the ratio of the friction force to normalforce.

Members 29 may be provided to displace a portion of the oil being testedthereby to reduce the volume of the oil in the container 14.

FIG. 3 shows a diagram with two coefficient of friction characteristiccurve 27 and 28. If the coefficient of friction characteristic curve 27extends progressively in a working range 26, the lubricant is suitablefor use in slip-controlled clutches. But if the friction characteristicvalue 28 progressively drops, self-excited oscillations are to beexpected in the use of the vehicle so that the lubricant is inadequatefor use in this case.

To prevent the test oil from overheating under the ring disc 6, which onthe contrary remains at a uniform temperature, there are provided in thespecimen holder 10 and in the main body 9, as well as, in the ring disc6 and the thrust washer 5, oil ducts 12 through which the test oil iscirculated in direction of the arrow 23 from an oil inlet 24 to an oiloutlet 25. The circulation effect is produced by centrifugal force inthe parts of the rotary oil ducts 12 which extend substantiallyradially.

Owing to the simple structure and the small amount of test oil requiredfor a measured value series, the expense for the measurements can bekept within reasonable limits during a service life cycle. The smalltest oil removal allows fatigue tests to be continued without impairmentso that measurement results of assertive force are obtained for theentire service cycle.

    ______________________________________                                        Reference numerals                                                            ______________________________________                                                  1 motor                                                                       2 torque indicator                                                            3 equalizer connection                                                        4 input shaft                                                                 5 thrust washer                                                               6 ring disc                                                                   7 ring surface                                                                8 fiction lining                                                              9 main body                                                                  10 specimen holder                                                            11 peak bearing                                                               12 oil ducts                                                                  13 oil level                                                                  14 test container                                                             15 test board                                                                 16 torque support                                                             17 dynamometer device                                                         18 lever mechanisrn                                                           19 foundation                                                                 20 load delivery system                                                       21 bolt                                                                       22 bolt                                                                       23 arrow                                                                      24 oil inlet                                                                  25 oil outlet                                                                 26 working range                                                              27 friction characteristic curve                                              28 friction characteristic curve                                              29 displacement body                                                          30 axis                                                              ______________________________________                                    

What is claimed is:
 1. A process of ascertaining the lubricant power oflubricant in controlled slip clutches, comprising the steps of:a)providing a test device comprising a test container (14) in which is afirst member (6) rotatable by a motor (1) relative to a second member(9), the second member (9) being non-rotatably supported in thecontainer (14) on a bearing (11) and abutting the first member (6) at anannular friction interface (7, 8), and a load delivery system (18, 19,20) for urging the second member (9) and the first member (6) intomutual engagement at the interface (7, 8); b) placing a quantity of testoil in the container (14) to immerse at least the second member (9) andthe interface (7, 8); c) applying a test load to the second member (9)to urge the second member (9) into engagement with the first member (6)at the interface (7, 8) and rotating first member (6) relative to thesecond member (9); d) allowing the oil to reach a test temperature; e)measuring the applied load and torque transmitted by the frictionalengagement and calculating therefrom the coefficient of friction of therelatively rotating parts.